Connection flanges normally provide a planar interface between structural and/or fluid communication and containment elements. However, a planar interface does not provide self-centering. Centering has been achieved with body-bound bolts with tight clearance, but this can cause stuck bolts and differential expansion stress. Spigots have been used in which a component has an annular lip that is received in the end of an opposed component for centering. Standardized planar flange interfaces also allow unauthorized third party components to be used in an assembly.